Atopic dermatitis (AD) is a chronic, relapsing, pruritic skin disorder that generally first appears in childhood and frequently progresses to asthma and/or allergic rhinitis in the adult (Hanifin et al., Acta Dermatovener (Stockholm) Suppl 1980; 92:44-47; Leung et al., Dermatology in General Medicine, 4th edition, 1993, pp. 1543-1564; Cooper, J Invest Dermatol 1994; 102:128-137). There are no reliable laboratory markers for this condition but AD patients often have elevated serum IgE levels, allergic reactivity to foods and to other common allergens such as pollens, molds, and insects. There have also been reports of antinuclear antibodies (ANAs) in this condition (Taniguchi et al., Acta Derm Venereol (Stockh) Suppl 1992; 176:62-64; Tada et al., Dermatol 1994; 189:38-40). The prevalence of AD appears to be on the rise, with 10-15% of the population being affected at some time during childhood (Beltrani, J Allergy Clin Immunol 1999; 104:587-598; Leung, J Allergy Clin Immunol 1999; 104: S99-S108). We now report the finding of an autoantibody-autoantigen system in 30% of patients with AD which is also shared to a lesser extent by patients with asthma and interstitial cystitis (IC). IC is a urinary bladder condition in which the classical pathology is characterized by predominant mononuclear cell infiltration of the lamina propria with lymphocytes, plasma cells and mast cells (Gillenwater, et al., J Urol 1988; 140:203-206).